This invention relates to apparatus for feeding sheets and in particular to the prevention of double feeding. It is particularly advantageous for feeding banknotes.
In one known method of feeding sheets, a suction pick-up device pivots to lift a front sheet from a stack of sheets to be fed. When the sheets (for example banknotes) are in poor condition, it is more difficult for the suction pick-up to feed them singly. For this reason, in sheet-feeding machines of this kind, we have for many years incorporated a separating spring or plate which is normally attached to the stack holder and which is bent so that its end extends into the path of the leading end of the sheet. When the leading end of the sheet encounters the end of the spring or plate, it is momentarily retained by the spring or plate; the suction pick-up continues to move and the sheet therefore assumes a bowed condition. This continues until the end of the note clears the end of the spring or blade. At this point, the leading edge of the sheet is "flicked", i.e. it is subjected to a sudden movement as it rides over the end of the spring or plate.
Such an arrangement greatly reduces the number of double feeds and we have found that the double feeds which still occur vary with the rate of sheet feeding.
Sheet feeding apparatus according to the present invention, comprises: a housing; a cassette for a stack of sheets, movable into and out of the housing to and from a sheet feeding position; and a sheet feeder mounted in the housing and including means for lifting sheets one by one from the stack in the cassette and for advancing each sheet in turn away from the stack; the cassette including an adjustable separator the tip of which, when the cassette is in the sheet-feeding position, extends into the path of an edge of a sheet as the sheet is lifted away from the stack;
and is characterized by control means mounted in the housing so as to project into the path which is taken by the separator when the cassette is moved into the housing to the sheet-feeding position, the extent of such projection having one of at least two possible values, each corresponding to a different feed rate of the sheet feeder, whereby when the cassette is moved into the housing the control means automatically displaces the separator tip to cause it to project, to an extent depending upon the feed rate, into the path which will be followed by the said edge of a sheet lifted from the stack by the pick-up device.
The invention is based on our discovery that to reduce to a minimum the number of double feeds the amount by which the tip of the separator extends into the path of the fed sheet should vary with the rate of feeding of the sheets. At high rates of feeding of the sheets, the separators are required to extend further into the feed path.
Preferably, when the amount by which the separator extends into the feed path is changed, the angle presented by the separator to a fed sheet is also changed.
In one embodiment of the invention, an electromechanical system recognises the required rate of feed of the feed module and initiates a mechanism in the feed module to adjust the separator accordingly.
In order that the invention may be better understood, two embodiments of apparatus designed for feeding banknotes will now be described with reference to the accompanying drawings, in which: